1. Field of the Invention
The present invention relates generally to the testing of electrical signals, and more particularly, to an improved implementation for enabling testing of signals, such as small computer system interface (SCSI) signals, under various conditions.
2. Description of the Related Art
At present, various types of personal computer systems are in wide use. Such systems may be designed to incorporate hard disk drives (HDDs) and one or more input/output (I/O) devices, such as printers, scanners and the like. These devices are typically capable of external connectivity via a port connector. One of the common interfaces employed to connect I/O devices to a computer system is the small computer system interface (SCSI), for which standards have been established by the American National Standards Institute (ANSI). Since currently there are various SCSI file type devices such as HDDs, CD-ROMs, and magneto-optic (MO) discs, the SCSI is considered the standard in this field. A device that has an interface conforming to the SCSI is called a SCSI device, and a bus that can be connected to a SCSI interface is called a SCSI bus. Electrical signals transmitted in environments having SCSI devices and buses may be referred to as SCSI signals.
In environments employing electrical devices such as SCSI devices, it is important to understand signal characteristics in the environment. For example, it is important to have knowledge of certain electrical parameters such as signal amplitude, intersymbol interference, slew rates and/or signal skew. Knowledge of these parameters may assist in tasks such as product design and systems engineering. For example, knowledge of these parameters may assist in understanding how certain devices that communicate using SCSI signals such as servers, signal expanders and/or other devices operate under various conditions, and/or whether such devices comply with various standardized signal transfer protocols. This knowledge may also be used to determine what types of cables and/or devices are suitable for implementation in given environments and/or configurations. Accordingly, there is a need to perform signal testing with various types of signals such as SCSI signals.
To ensure wider test coverage, such testing should preferably be conducted under various conditions using several different testing configurations. Current signal testing techniques tend to be rather slow and laborious. In particular, separate tests must be run for each testing configuration and test cables must be manually located and changed for each test. This requires a user to engage in the time-consuming process of locating the necessary cables, and connecting the cables to the various devices in the testing configuration. Repeating this process for each testing configuration is especially burdensome. Accordingly, there is a need for a signal testing implementation which is faster, easily repeatable and enables wider test coverage. The present invention has been contemplated to address these and other problems.
The present invention provides a signal testing implementation which enables significant advantages over conventional signal testing techniques. According to an exemplary embodiment, an apparatus for enabling signal testing such as SCSI signal testing in a test configuration provides a cable environment embodied as a portable housing structure including a plurality of cables exhibiting a plurality of lengths and impedances. At least a portion of each of the cables is supported within the portable housing structure. A user can selectively connect any one of the cables between a host device such as a server and a target device such as a disk subsystem. According to an embodiment, a user can select a particular cable for connection between the host device and the target device through input to a switch. Signal measurement connectors which are connectable to the portable cable environment may be provided. Each of the signal measurement connectors includes one or more test measurement points to enable collection of signal testing results. In use, the portable cable environment can be moved to a location corresponding to a given test configuration. A user can then selectively connect any one of the cables of the portable cable environment between the host device and the target device.